1. Field of the Invention
This invention is related to memory systems for computer systems, and specifically to power and performance in memory systems.
2. Description of the Related Art
Reducing the power consumed by computer systems of various types has quickly becoming a focus for computer system manufacturers. For example, mobile devices such as laptops, cell phones, personal digital assistants (PDAs), etc. are common and battery life can be extended by reducing the power consumption. Server-class computers are frequently deployed in rack mounts and other configurations which place the computers in close proximity to each other and other devices. Because the heat (a function of the power consumed) is challenging to dissipate in such configurations, the power consumed in the computer is a concern for these computers as well.
In the past, the focus has been on reducing the power consumed by processors in the computer systems. However, as the size of the main memory system has grown and the clock frequency of the synchronous dynamic random access memories (SDRAMs) used to populate the main memory system has increased, the power consumed in the main memory system has become a larger factor in overall system power consumption. Modern SDRAMs implement various power modes, with increasing amounts of power saved but also increasing latencies to exit the low power mode. Selecting which power mode is best for a given application is unclear.